Unfortunately I could not get my USB flash-drive to boot using these instructions. I didn't try setting the 'boot' flag mentioned by eugnevandermerwe - that probably does the trick.

I also ran into write issues when trying to copy my BIOS update files to the device (Linux Mint 18.3). This should get around that:
sudo umount /media/[USER]/[DEVICE_LABEL]
sudo mount -o rw,users,umask=000 /dev/sdb1 /mnt